1. Field of the Invention
The invention relates to a working chair with a seat, a back and a lower frame, of which the frame comprises a vertical supporting pillar adjustable as to height and a carrier frame connected with the upper end of said pillar. The seat is pivotally connected with the carrier frame in the proximity of its front edge by a first pivot connection with a horizontal axis of rotation. The first pivot connection comprese a pivot pin connected with the seat or the carrier frame, the other of the seat and the carrier frame being provided with a track inclined with respect to the horizontal for allowing a substantially translatory movement of the seat perpendicular to the axis of rotation with respect to said carrier frame. A mounting arm in firm connection with a back support connected with the back is pivotally connected with the carrier frame as well as with the seat by second and third pivot connections having axes of rotation mutually parallel and parallel with the axis of said first pivot connection. The pivot connections are designed for synchronous movement of the seat and the back, whereby the seat from a backwards inclining rest position by rotation in said first pivot connection may be moved to a working position and the back synchronously therewith may be moved from a backwards inclining extreme position in which it forms a maximum angle with the seat towards a more upright position while gradually reducing its angle with the seat.
2. Prior Art
From EP-A-0418731 such a working chair is known in which the seat can be moved between a backwards inclining rest position and a working position in which the seat is horizontal and forms an angle of approximately 90xc2x0 with the back support.
It is known to design a working chair of the type referred to with an extended range of variation of the seat inclination so that the seat angle with respect to horizontal may be adjusted from the backwards declining rest position to a forwards declining supporting position for the user in a more erect position.
In connection with such an extended range of adjustment in relation to conventional working chairs it is, moreover, known to provide a working chair of the kind concerned with a synchronous mechanism which automatically sets the angular adjustment of the back support in relation to the seat, typically so that the angle between the seat and the back support increases the more the seat inclines backwards, conversely it, decreases when the seat from the backwards inclining rest position is moved towards the forwards inclining supporting position.
In some known synchronous chairs with the last mentioned possibility of adjustment a continuous diminishing of the seat-back angle is effected throughout the range of adjustment of the seat from the backwards declining rest position to the forwards declining supporting position, so that said angle in the forwards declining extreme position of the seat is smaller than in the neutral position of the chair, in which the seat plane is substantially horizontal.
This continuous reduction of the seat-back angle has, however, shown to be a disadvantage when using the chair because the user typically has the feeling that the seat and back collapse during the adjustment movement after the neutral position has been passed.
To eliminate this disadvantage and thereby obtain an increased seat angle with the horizontal in the forwards right extreme position the Applicant has further developed a chair with a design of the synchronous mechanism which causes that the seat-back angle during the adjustment movement assumes its minimum value in the proximity of said neutral position with a substantially horizontal seat plane, but increases again from said minimum value while continuously adjusting the seat towards the forwards declining extreme position.
The object of the invention is to provide a further development of a synchronous chair with the last mentioned usefully advantageous variation of the seat-back angle during the adjustment movement so that an automatical setting of the seat depth is effected as well so that this increases at forwards as well as at backwards declination of the seat.
This is obtained according to the invention in that the track is directed obliquely upwards towards the front edge of the seat and is inclined at an angle of 40xc2x0 to 70xc2x0 with the vertical axis of the supporting pillar to provide a range of said translatory movement by which the seat is movable from said backwards declining rest position in which the front edge of the seat is displaced backwards and downwards with respect to the carrier frame to a forward declining extreme position, in which the front edge of the seat is displaced forwards and upwards with respect to the carrier frame.
By the displacement thus obtained of the seat front edge a better comfort for the user is obtained, since the front edge of the seat during movement from the backwards declining to the forward declining seat position will be displaced forwards and upwards while preserving complete back support, thereby adapting the height of the seat front edge above the floor to the user""s more erect position. Correspondingly, during the opposite movement from the forward declining to the backwards declining seat position the seat front edge will be displaced backwards and downwards, thereby adapting the seat front edge to the opening of the angle between user""s thighs and crus taking place during the backwards movement, thereby reducing the pressure of the seat front edge against the back of user""s thighs. Both adjustment movements may thus be effected by the user at maximum comfort and with no change of his position on the seat and the user does not need to lift his feet from the floor.
To facilitate the adaptation of one and the same working chair to users of different height a comparatively simple adjustment mechanism may according to a further development of the invention be provided for simultaneous adjustment of the seat depth and the back height of the chair the back support comprises two substantially rectilinear parts forming an obtuse angle with each other, one of said parts being substantially vertical and connected with the back whereas the other is mounted in a back support holder positioned under the seat and connected with the carrier frame in such a manner that by means of an arrestable operating element it may be displaced in its longitudinal direction and maintained in various adjustments in said back support holder for simultaneous adjustment of the seat depth and the height adjustment of the back in relation to the seat.
Various further modifications of the working chair exist and will be described herein.